Smartphone: Droid X2, Gingerbread App involved: K-9 I discovered today that the K-9 android email client apparently uses the "content-type" tag in an email for an attachment to find out what app to use to open the attachment. Here's what happened: an email was sent out from a server-based proposal system (Pursuit 7, in fact) with a PDF attachment. We opened the email in K-9, and we then attempted to open the PDF attachment, but K-9 said "Unable to find viewer for application/x-unknown". I then manually sent out an email from my laptop (using Thunderbird) with this exact same PDF attached. We opened this email in K-9 and were able to open the PDF attachment with no problem (it gave us a choice of Adobe Reader or QuickOffice, BTW, just like normal). I looked into the internal source code of the first email and it had this: Content-Type: application/x-unknown; name="PROPOSAL1001293.PDF" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="PROPOSAL1001293.PDF"; size=8922 Next, I looked into the internal source code of the second email and it had this: Content-Type: application/pdf; name="PROPOSAL1001293.PDF" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="PROPOSAL1001293.PDF"; size=8922 I don't think the Pursuit 7 software vendor is going to fix their email engine, so I'm trying to find a way to work around this with K-9. If K-9 would use the attachment's extension (".pdf") instead of the content-type tag then there would be no problem. Any ideas, anyone? PS: Does K-9 have a support forum? I can't seem to find one. Thanks.